Telephone-receiver.



UNITED PATENT OFFICE.

ABNER F. H. DAVIS, OF OAKLAND, CALIFORNIA, ASSIGNOR TO THE NATIONAL TELEGRAPHON l COMPANY, OF

ROCHESTER, NEW

YORK, A CORPORATION OF THE lJlSlltlGT OF COLUMBIA.

TELEPHONE-RECEIVER.

Specification of Letters Patent.

Patented May 14, 1907.

To all whmn it may concern:

Be it known that 1, Anson F. H. DAVIS, a citizen of the United States of America, and a resident of Oakland, county of Contra Costa, and State of California, have invented certain new and useful Improvements in Telephone- Receivers, of which the following is a specification.

My invention relates to improvements in telephone receivers, and has for its object the altering of the instrument in a mariner to benefit its talking qualities, and to permit its use under conditions, which are unfavorable to, or prohibit the employment of the ordinary telephone receiver. Such conditions i have found to exist upon many lines, over which it is desirable to conduct simultane ousl y telegraphic and telephonic communication.

Viherc composite telephony and telegraphy are attempted, it is well known that the te ephonic transmission is subjected to very adverse inductive conditions. Moreover, the lines are grounded and have connected therein, numerous electro-magnetic or relay windings; all of which contribute to impair or destroy tele honiccommunication.

It is perfect y obvious that with a proper transmitter and battery circuit, voice-currents may be impressed upon a given line, hence it follows that the receiver must be adapted to the varying conditions of use. Accordingly, I have im roved the telephonic receiver in a manner a apting it for satisfactory use under what are normally found to be adverse conditions. These improvements, I may briefly indicate as consistin of an improved censtruction, involving tlle use of a non-magnetic diaphragm for the receiver, which diaphragm preferably is formed of metal affording relatively good paths for the induced electric currents, if I correctly apprehend the theory of operation. For such diaphragm, I mayuse a disk or plate of aluminium, or brass or a thinner one of hard-drawn copper or silver, for example. In connection with said diaphragm, I may employ means for closing the magnetic circuit therethrough from the poles of the electro-magnet of the receiver, and means for adjusting the position of the diaphragm. These details of my improvement, however, will he understood as being independent of my invention in its broader as set. FUIthBIII'LOIO, 1 preferably make the e ectro-magnet windings of the re ceiver of low resistance.

Further details may be more readily gathered, by making reference to the accompanying sheet of drai-vings, wherein;

Figure 1, of the drawings is a horizontal sectional view of a telephone receiver, made in accordance with my invention, 1* ig. 2, is an enlarged view, showing means for effecting the close adjustment of the diaphragm, with respect to the electro-magnet. Fig. 3, is a detail, partly broken away, illustrating means for concentrating the flow of the mag netic lines of force through the body of the diaphragm; and Fig. 4, is an interior view of the modified receiver-cap.

The same character of reference is employed throughout each of the several ligures of the drawings to designate similar parts.

Figure 1 illustrates the general features of a telephone receiver in common use, in which my improvement is employed. Within the hard rubber casin r c, is mounted the permanent magnet m, 51sec extended poles p are co-incident with those of the electro-magnets e. The windings of the electromagnet are connected in circuit to be traversed by the transmitted V tele honic voice-currents A shell 8 is th reade upon the extension of the magnet m, so as to be adjustable with respect to the extremities of the poles p; a nut s, holding the shell in its adjusted position. This improvement, securing an adjustment of the diaphragm, with respect to the magnet-poles, may Well be omitted, if desirer since the ordinary non-adjustable receiver usually is found to be entirely satisfactory, when equipped with my non-magnetic diaphragm.

Carried upon the outer rim of the shell s, is the diaphragm d of my invention; This, I may form of aluminium, brass, or of a relatively thinner sheet of hard drawn copper, or other suitable non-magnetic metal, The cap 6 screws down upon the diaphra m and holds it closely against the shell in position before the poles of the electrdniagnet. It will he understood that a much closer positioning of the diaphragm, with respect to the poles of the electro-magnet, is permissible, where the diaphragm is non-magnetic. It may be desirable to shellac, and thus insu- LOO late the presented ends of the poles p. Vith an instrument constructed in this manner, it will be found that the inductive ell'eets of electrical currents connnonlyinipairing transmission, are materially modilied or elimi nated, so far as the receiving qualities of my improved instrument are concerned. 'lhus with telegraphic lines of more than ordinary length, wherein a large number of relays are connected, and over which lines hitherto it has been found impossible to carry on telephonic conversation, I have been able to secure satisfactory commercial transmission. Accordingly, I believe that my improvement is such as to eliminate practically the effects of electric currents, other than tBlGPl'lOlliC voice-currents, and sharply define the transmitted sound-waves under conditions ordinarily impossible, thereby greatly improving the usefulness of the receiver.

As I understand the operation, the diaphragm in my improved receiver, instead of being n'iagnetically affected by the trans mitted currents, depends for its action upon the production therein of Foucault or eddycurr *nts, thus in effect, making the body of the metal thereof, the secondary of an induction coil. Accordin ly, it is desirable that the electrical resistance shall be low and that the maximum lines of force shall cut the diaphragm. Again, the battery should be strong. Vvhile I do not represent that the receiver of my invention is fully adapted for use upon the average telephone-line, owing to the somewhat reduced theoretical. and den'lonstrated efficiency, as compared with the ordinary receiver, still this difference may be largely overcome, as by properly adjusting the battery.

To secure the adjustment of the diaphragm, the shell is turned up and down upon its threaded support; while to concen trate the lines of force through the body of the armature, I may position a mass of mag netic material, such as the perforated iron plate i, within the cap 0 of the transmitter, but out of contact with the diaphragm. This plate 2' serves as a low resistance path for the lines of force, and is a desirable adjunct, under some circumstances for increasing the efliciency of a non-magnetic diaphragm for telephone receivers.

have found that the best results are secured in a telephone receiver employing my invention wherein the magnet windings are of low resistance; employing for this pur pose receivers wound to have resistances even as low as one ohm. Moreover, when employed upon lines over which simultaneous telephony and telegraphy are conducted, I have found it desirable to connect such. receiver serially in circuit with the associated telephone transmitter.

W hile I have suggested herein several features or adjuncts which may be associated with my improvenients, l consider that the use of a receiver-diaphragni of a suitable nonmagnetic constitutes the most in|- port ant feature sought to be covered herein, for the purpose of preventing inductive disturbances from adjacent electrical systems of any character whatsoever.

laving now set forth an embodiment of my inventioi'i and the preferred uutterials for forming the diaphragm and its auxiliary 'larts, I claim as new and desire to secure by Letters Patel'it, the following2-- 1. The combination. with an electro-magnetic telephone receiver, of a diaphragm therefor comprising solely a plate or disk of non-magnetic material, of relatively high electrical conductivity, substantially as set forth.

2. The combination with an electro-magnetic telephone receiver, of a diaphragm therefor comprising a plate or disk of nonmagnetic material, of relatively high elec trical coi'iductivity, and means for closing the lines of magnetieforce within the non-magnetic body of the diaphragni, substantially as set forth.

3. In a telephone receiver, a diaphragm formed solely of non-magnetic material, such as aluminium or brass, and an exciting electro-ma net positioned adjacent thereto, substantia ly as set forth.

4. In a telephone receiver, the combination with the electro-mamet thereof, of a diaphragm positioned before the magnetpoles comprising a non-magnetic conductive plate or member unassociated with any vibrating magnetic member, substantially as set forth.

5. In a non-intluctively-affectod telephone receiver, the combination with the exciting electro-magnet having windings thereon of relatively' coarse wire to present a low resistance path for the telephonic currents, of a non-magnetic diaphragm positioned immeformed of brass or aluminium, and a l or casing for securely positioning the parts in proper association with each other, substantlally as set forth.

6. In a telephone receiver, a diaphragm formed of suitable non-magnetic material, an electro-magnet with its poles positioned adjacent thereto, and a detached magnetic body positioned to close the magnetic lines of force through the nonanagnetic diaphragl'n, substantially as set forth. 7

7. In a telephone receiver, a diaphragm formed of suitable non-magnetic material, an exciting electro-magnet with its poles positioned adjacent thereto, and a magnetic bridge-piece disposed beyond one side of the diaphragm opposite the poles of the electromagnet, and in position to close the lines of magnetic force therefrom, substantially as set forth.

S. in a! teiephune r'aaeiver, the :mmhinaflan with the ponn mvn i1 and 1lvctnymagnefs vl forth. thereof, of a diaphragm PUSitiUDEd inlfiwdi- Signed at Portland, Oregon this 4th day atel}; boibre the nmgnet pole-s COIllPFir-fiiig :1 5 Hf Nov. 1985.

' ABNER F. TI. DAVIS.

{ for pmducing s'mmd waves, substantially as s unassiiscmmd with any vibrating lnagneiinf \Yitnggsesg V msmbcr, through which :haphra'gm the fines J. GAITHN, of maguutxe fhrce an adapted to be closed 1 AK REID. 

